As electronic equipment is used at higher frequencies, a capacitor, i.e. one of the electronic components thereof, is required to have more excellent impedance characteristics in a higher-frequency range than conventional capacitors. To meet such a requirement, a solid electrolytic capacitor using conductive polymer having high electric conductivity as a solid electrolyte thereof is studied.
Additionally, there have recently been strong demands for a smaller solid electrolytic capacitor with higher capacity that is to be used around the CPU of a personal computer. Further, to support higher frequencies, there are strong demands for excellent ability of noise reduction and transient response, and reduction in equivalent serial inductance (lower ESL) as well as reduction in equivalent serial resistance (lower ESR). Various studies are conducted to satisfy these demands.
FIG. 9 is a perspective view illustrating a structure of a conventional chip type solid electrolytic capacitor. FIG. 10 is an exploded perspective view illustrating an inner structure thereof. Capacitor elements 20 including a conductive polymer as a solid electrolyte thereof form a major portion of the solid electrolytic capacitor. Each capacitor element 20 includes anode portion 21, cathode portion 22, and insulator 23. Two capacitor elements 20 structured as above are placed one on the other in the direction opposite to each other.
One end of anode lead terminal 24 is connected to anode portion 21. One end of cathode lead terminal 25 is connected to cathode portion 22. Exterior resin 26 molds these components. In this manner, the solid electrolytic capacitor is formed. Anode lead terminals 24 and cathode lead terminals 25 are exposed from the side faces and the bottom face, respectively, of the solid electrolytic capacitor to face each other. Thus, the solid electrolytic capacitor having a four-terminal structure is formed.
The conventional chip type solid electrolytic capacitor structured as above is excellent in high-frequency characteristics and noise-absorbing ability, and capable of achieving lower ESL. Such a chip type solid electrolytic capacitor is disclosed in Unexamined Japanese Patent Publication No. H06-120088, for example.
However, for the conventional chip type solid electrolytic capacitor, reduction in ESL is limited to approx. 500 pH. In other words, the conventional one is still insufficient to satisfy a level of 200 pH or lower, which is required in the recent market, and requires further reduction in ESL.